The original pneumatic tire was developed in 1888 based on the observation that a flexible tire that conforms to the ground does not lose as much energy to vertical motion as a rigid wheel. There is a net energy savings when the tire contours to variations in topography as compared to simply driving over them. This feature also provides a smoother ride in a vehicle equipped with such a tire. However, because of their reliance on a constant air pressure, pneumatic tires suffer from efficiency loss due to pressure changes, and are prone to going flat when punctured. More recently, various non-pneumatic tire concepts have been developed. These non-pneumatic tires are typically limited in their ability to conform to the terrain without damage.